1. The Field of the Invention
Implementations of the present invention relate generally to drilling tools that may be used to drill geological and/or manmade formations. In particular, implementations of the present invention relate to impregnated cutting elements with large abrasive cutting media, such as polycrystalline diamonds embedded therein, as well as methods for making and using such drill bits.
2. The Relevant Technology
Drill bits and other drilling tools can be used to drill holes in rock and other formations for exploration or other purposes. For example, a drill bit can be attached on the lower end of a drill string (i.e., a series of connected drill rods coupled to a drill head). A drill head or downhole motors, or both, can then rotate the drill string, and in turn the drill bit. A downward force can then be applied to the drill bit, which can cause the drill bit to engage the formation and form a borehole within the formation.
The type of drill bit selected for a particular drilling operation can be based on the type and hardness of the formation being drilled. For example, surface-set bits or drill bits having fixed cutters can be used to drill soft to medium-hard formations. The fixed cutters or inserts of these drill bits can be designed to penetrate quickly due to the depth of cut per revolution. One commonly used type of fixed cutter is a polycrystalline diamond compact (PDC) insert. The PDC inserts are often distributed along the cutting face of the drill bit in specific orientations and positions. While surface-set or fixed cutter drill bits can provide various benefits, because the inserts typically only include a single layer of diamond, the life of such drill bits can be limited.
Furthermore, in drilling hard and/or abrasive formations, surface-set bits can be ineffective or inefficient. Thus, for harder formations, impregnated drill bits with renewable cutting elements are typically preferred. Impregnated drill bits typically include a cutting portion or crown that may include a matrix containing a powdered hard particulate material, such as tungsten carbide and/or other refractory or ceramic compounds. The hard particulate material may be sintered and/or infiltrated with a binder, such as a copper-based alloy. Furthermore, the cutting portion of impregnated drill bits may also be impregnated with an abrasive cutting media, such as natural or synthetic diamonds.
During drilling operations, the abrasive cutting media is gradually exposed as the supporting matrix material is worn away. The continuous exposure of new abrasive cutting media by wear of the supporting matrix forming the cutting portion can help provide a continually sharp cutting surface. Additionally, as the entire crown may function the cutting element as it erodes during drilling, impregnated drill bits can have an increased cutting life. Impregnated drill bit may continue to cut efficiently until the cutting portion of the tool is consumed. Once the cutting portion of the tool is consumed, the tool becomes dull and requires replacement.
While impregnated drill bits can be effective and efficient in drilling harder formations, they may be ineffective or inefficient in drilling soft formations due to the size of abrasive material used in impregnated bits. Along similar lines, while surface-set bits can be effective and efficient in drilling softer formations, they may be ineffective or inefficient for drilling hard and/or abrasive formations. Thus, when drilling formations that contain both hard and soft regions, it may be desirable to switch between a surface-set bit and an impregnated drill bit. The replacement of a drill bit requires removing (or tripping out) the entire drill string out of a borehole. Once the drill bit is replaced, the entire drill string typically is then assembled section by section and then tripped back into the borehole. Switching a drill bit can be time consuming, difficult, and potentially dangerous.
Accordingly, there are a number of disadvantages in conventional drill bits that can be addressed.